The purpose is to investigate the abilities of the deaf, and of other persons with impaired hearing, to perceive various qualities of complex auditory stimuli. The method is to compare abnormal and normal audition using tests of discrimination and identification of specially designed sound stimuli having known acoustical characteristics. The comparisons are made so as to develop new psycoacoustic information on the perceptual effects of neuro-sensory pathologies of audition. Discrimination and identification measures are carried out for known timbre differences among vowel sounds, simulated consonant sounds, and sound spectral patterns which vary in time, such as formant transitions and the spectral properties of noise-like bursts adjacent to vowel sounds.